1. Field of the Invention
Embodiments relate to a polishing slurry composition.
2. Description of the Related Art
With a decrease in design rules for products, a width decreases and a height increases in a structure, and accordingly an aspect ratio, that is, a depth/bottom width ratio is drastically increasing. Also, an influence of scratches occurring in a 30-nanometer semiconductor process is at least two times higher than an influence of scratches occurring in a 50-nanometer semiconductor process according to a related art. Thus, not only scratches but a planarization degree also has sensitive effects on a surface of a film. A polishing amount and a quality of a polished surface are regarded as crucial factors in a polishing process. Importance of a quality of a polished surface is maximized based on a decrease in design rules for semiconductors in recent years, and accordingly a polishing process for the quality of the polished surface tends to be added.
Recently, lower current leakage is required based on an increase in integration of a semiconductor. To satisfy such a requirement, a structure of a dielectric with a high dielectric constant and a metal gate is designed. Generally, aluminum is frequently used as a metal gate material. The decrease in design rules makes it difficult to completely deposit and polish aluminum oxide with a high hardness, and thus extensive studies on use of tungsten as a gate material are recently conducted. However, as a constituent material of a gate is changed from aluminum to tungsten, tungsten topographies are formed due to a particle size of tungsten crystals after deposition, which causes an undesired short circuit between metals to reduce a semiconductor yield. To improve a quality of a polished surface of tungsten, that is, to improve a planarization degree, polishing is essential for a next-generation process. A slurry composition in which a planarization degree is not improved causes over-etching or un-etching of tungsten in a post-polishing process to bring about process defects or to make an operation of a device unstable, thereby drastically reducing a semiconductor yield. In addition, because most slurry compositions for polishing tungsten according to a related art are designed to be optimized for a polishing amount or a selectivity with titanium and silicon oxide films, the slurry compositions have a relatively low planarization degree.